DNA sequences with oligosaccharide transporter, plasmids, bacteria and plants containing a transporter as well as a process for the preparation and transformation of yeast strains for identification of the transporter

ABSTRACT

There are described DNA sequences, that contain the coding region of an oligosaccharide transporter, whose introduction in a plant genome modifies the formation and transfer of storage materials in transgenic plants, plasmids, bacteria and plants containing these DNA sequences, a process for the preparation and transformation of yeast strains, that makes possible the identification of the DNA sequences of the plant oligosaccharide transporter of the invention, as well as the use of DNA sequences of the invention.

FIELD OF THE INVENTION

The present invention relates to DNA sequences, that contain the coding region of an oligosaccharide transporter, whose introduction in a plant genome modifies the formation and transfer of storage materials in transgenic plants, plasmids, bacteria and plants containing these DNA sequences, a process for the preparation and transformation of yeast strains, that makes possible the identification of the DNA sequences of the plant oligosaccharide transporter of the invention, as well as the use of DNA sequences of the invention.

BACKGROUND OF THE INVENTION

The most important transport metabolite for stored energy in many plants, for example potatoes, is sucrose. In other species, other oligosaccharides can serve this role. In Japanese artichokes for example it is stachyose.

The central position of the oligosaccharide transport in the energy content of the plant has already been shown in transgenic plants, in which by expression of an invertase, the sucrose is split into the monosaccharides, leading to considerable changes in its habit (EP 442 592). Because of the significance of sucrose in the formation of storage materials, numerous experiments have been carried out into investigating the biosynthesis or the metabolism of disaccharides. From DE 42 13 444, it is known that the improvement of the storage properties of the harvested parts can be achieved in transgenic potatoes, in which through expression of an apoplastic invertase, the transfer of energy rich compounds to the heterotrophic parts of growing shoots is inhibited.

In spite of much effort, the mechanism for distributing storage materials, such as oligosaccharides in plants has not been clarified and, in order to influence it, it is not yet known, how the sucrose formed in the leaves following photosynthesis, reaches the transport channels of the phloem of the plant and how it is taken up from the storage organs, e.g. the tubers of potato plants or seeds. On isolated plasma membranes of cells of leaf tissue of sugar beet (Beta vulgaris) it has been demonstrated that the transport of sucrose through the membrane can be induced by providing an artificial pH gradient and can be intensified by providing an electrochemical potential (Lemoine & Delrot (1989) FEBS letters 249: 129-133). The membrane passage of sucrose follows a Michaelis-Menten kinetic, in which the k_(m) value of the sucrose transport is around 1 mM (Slone & Buckbout, 1991, Planta 183: 484-589). This form of kinetic indicates the involvement of transporter protein. Experiments on plasma membranes of sugar beet, Ricinus communis and Cyclamen persicum has shown that the sucrose transport is concerned with a cotransport of protons (Buckhout, 1989, Planta 178: 393-399; Williams et al., 1990, Planta 182: 540-545; Grimm et al., 1990, Planta 182: 480-485). The stoichiometry of the cotransport is 1:1 (Bush, 1990, Plant Physiol 93: 1590-1596). Mechanisms have also been proposed however, for transport of the sucrose through the plasmodium of the plant cells (Robards & Lucas, 1990, Ann Rev Plant Physiol 41: 369-419). In spite of the knowledge of the existence of an active transport system, that allows the cells to deliver sucrose to the transport channels, a protein with these kind of properties is not yet known. In N-ethylmaleinimide staining of sugar beet plasma membrane in the presence and absence of sucrose Gallet et al. (1989, Biochem Biophys Acta 978: 56-64) obtained information that a protein of size 42 kDa can interact with sucrose. Antibodies against a fraction of plasma membrane protein of this size range can inhibit the sucrose transport through plasma membranes (Lemoine et al., 1989, Bichem Biophys Acta 978: 65-71). In contrast, information has been obtained (Ripp et al., 1988, Plant Physiol 88: 1435-1445) by the photoaffinity marking of soyabean protein with the sucrose analogue, desoxyazidohydroxybenzamidosucrose, on the participation of a 62 kDa protein in the transport of sucrose through membranes. An amino acid sequence of a sucrose transporter is not known.

SUMMARY OF THE INVENTION

There are now described DNA sequences which contain the coding region of an oligosaccharide transporter, and whose information contained in the nucleotide sequence allows, by sequence integration in a plant genome, the formation of RNA, by which a new oligosaccharide transport activity can be introduced in the plant cells or an endogenous oligosaccharide transporter activity can be expressed. By the term oligosaccharides transporter is for example to the understood a sucrose transporter from plants such as spinach or potatoes.

The identification of the coding region of the oligosaccharide transporter is carried out by a process which allows the isolation of plant DNA sequences which code the transporter molecules by means of expression in specific mutants of yeast Saccharomyces cerevisiae. For this, suitable yeast mutants have to be provided which cannot take up a substance for which the coding region of a transporter molecule has to be isolated from a plant gene library. A process is already known for complementation of a potassium transport deficiency in yeast mutants (Anderson et al., 1992, Proc Natl Acad Sci USA 89: 3736-3740). In this, yeast cDNA sequences for plant mRNA are expressed in yeast mutants by use of expression vectors. Those yeasts which can now take up the substances to be transported into the cells, contain the coding region for a transporter molecule in the expression vector. The known process is however not useful for identification of the coding region for a sucrose transporter, since yeasts contain no endogenous sucrose transporter which could be switched off through mutation. Yeasts code a cleaving invertase, which cleaves extracellular sucrose so that hexoses can be taken up from the cells via a hexose transporter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the uptake of sucrose in yeast cells over time;

FIG. 2 shows the cloning of the plasmid pMA5-INV;

FIG. 3 is a diagram of the plasmid pBinAR-S21;

FIG. 4 is a diagram of the plasmid pBinAR-P62 -anti;

FIG. 5 is a graph of the content of various carbohydrates in the leaves of plants transformed with the plasmid BinAR-P62-anti; and

FIG. 6 is a graph of the efflux of carbohydrates from the petioles of plants transformed with the plasmid BinARP62-anti.

DETAILED DESCRIPTION OF THE INVENTION

For the preparation and transformation of yeast strains which serve to identify a plant oligosaccharide transporter:

a) first, a yeast strain with a defective suc2 gene, which cannot be cleaved by invertase, is prepared by homologous recombination and then from this,

b) by transformation with a gene for a sucrose synthase activity from plant cells, a yeast strain which can cleave intracellular sucrose is extracted, and

c) by transformation of this strain with a plant cDNA library in an expression vector for yeast cells, the DNA sequence, which codes for a plant oligosaccharide transporter, is identified.

The yeast strains obtained from this process, for identification of plant oligosaccharide transporters are for example the yeast strains YSH 2.64-1A-SUSY (DSM 7106) and YSH 2.64-1A-INV (DSM 7105).

With the yeast strain YSH 2.64-1A-SUSY, a DNA sequence for a plant sucrose transporter is identified which has the following sequences. ##STR1##

The identified DNA sequences can be introduced into plasmids and thereby be combined with steering elements for expression in eukaryotic cells (see Example 5). These steering elements are on the one hand transcription promoters, and on the other hand transcription terminators. With the DNA sequences of the invention contained on the plasmids, eukaryotic cells can be transformed, with the aim of expression of a translatable mRNA which makes possible the synthesis of a sucrose transporter in the cells or with the aim of expression of a non-translatable RNA, which prevents synthesis of an endogenous sucrose transporter in the cells. By expression of an RNA corresponding to the inventive sequences of the oligosaccharide transporter, a modification of the plant carbohydrate metabolism is possible, which can be of significance in that an improvement in the delivery of storage substances in the harvested parts results in an increase in yield of agricultural plants. The possibility of forcing the uptake of storage materials in individual organs allows the modification of the whole plant by which the growth of individual tissues, for example leaves, is slowed down, whilst the growth of the harvested parts is increased. For this, one can imagine a lengthening of the vegetative phase of crops, which leads to an increased formation of storage substances.

Processes for the genetic modification of dicotyledonous and monocotyledonous plants are already known, (see for example Gasser, C. S., Fraley, R. T., 1989, Science 244: 1293-1299; Potrykus, 1991, Ann Rev Plant Mol Biol Plant Physiol 42: 205-225). For expression in plants--the coding sequences must be coupled with the transcriptional regulatory elements. Such elements called promoters, are known (EP 375091).

Further, the coding regions must be provided with transcription termination signals with which they can be correctly transcribed. Such elements are also described (see Gielen et al., 1989, EMBO J 8: 23-29). The transcriptional start region can be native and/or homologous as well as foreign and/or heterologous to the host plant. If desired, termination regions are interchangeable with one another. The DNA sequence of the transcription starting and termination regions can be prepared synthetically or obtained naturally, or obtained from a mixture of synthetic and natural DNA constituents. For introduction of foreign genes in higher plants a large number of cloning vectors are available that include a replication signal for E. coli and a marker which allows selection of the transformed cells. Examples of such vectors are pBR 322, pUC-Series, M13 mp-Series, pACYC 184 etc. Depending on the method of introduction of the desired gene in the plants, other DNA sequences may be suitable. Should the Ti- or Ri-plasmid be used, e.g. for the transformation of the plant cell, then at least the right boundary, often however both the right and left boundary of the Ti- and Ri-Plasmid T-DNA, is attached, as a flanking region, to the gene being introduced. The use of T-DNA for the transformation of plants cells has been intensively researched and is well described in EP 120 516; Hoekama, In: The Binary Plant Vector System, Offset-drukkerij Kanters B. V. Alblasserdam, (1985), Chapter V; Fraley, et al., Crit. Rev. Plant Sci., 4:1-46 and An et al. (1985) EMBO J. 4: 277-287. Once the introduced DNA is integrated in the genome, it is generally stably incorporated and remains also in the offspring of the original transformed cells. It normally contains a selection marker, which induces resistance in the transformed plant cells against a biocide or antibiotic such as kanamycin, G 418, bleomycin, hygromycin or phosphinotricin etc. The individual marker employed should therefore allow the selection of transformed cells from cells which lack the introduced DNA.

For the introduction of DNA into a plant host cell, besides transformation using Agrobacteria, there are many other techniques available. These techniques include the fusion of protoplasts, microinjection of DNA and electroporation, as well as ballistic methods and virus infection. From the transformed plant material, whole plants can be regenerated in a suitable medium, which contains antibiotics or biocides for the selection. The resulting plants can then be tested for the presence of introduced DNA. No special demands are placed on the plasmids in injection and electroporation. Simple plasmids, such as e.g. pUC-derivatives can be used. Should however whole plants be regenerated from such transformed cells the presence of a selectable marker gene is necessary. The transformed cells grow within the plants in the usual manner (see also McCormick et al. (1986) Plant Cell Reports 5: 81-84). These plants can be grown normally and crossed with plants that possess the same transformed genes or different genes. The resulting hybrid individuals have the corresponding phenotypical properties.

The DNA sequences of the invention can also be introduced in plasmids and thereby combined with steering elements for an expression in prokaryotic cells. The formation of a translatable RNA sequence of a eukaryotic sucrose transporter from bacteria leads, in spite of the considerable differences in the membrane structures of prokaryotes and eukaryotes, to prokaryotes which are able to take up sucrose. This makes possible the production of technically interesting bacterial strains, which could be grown on the relatively cheap substrate sucrose (see Example 5). For example, the production of polyhydroxybutyric acid in the bacteria Alkaligenes eutrophus is described (Steinbuchel & Schubert, 1989, Arch Microbiol 153: 101-104). The bacterium only uses however a very limited selection of substrates. The expression of a gene for a sucrose transporter, amongst others, in Alkaligenes eutrophus would therefore be of great interest.

The DNA sequences of the invention can also be introduced in plasmids which allow mutagenesis or a sequence modification through recombination of DNA sequences in prokaryotic or eukaryotic systems. In this way the specificity of the sucrose transporter can be modified.

By using standard processes (see Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual, 2. Edn., Cold Spring Harbor Laboratory Press, N.Y., USA), base exchanges can be carried out or natural or synthetic sequences can be added. For binding DNA fragments with one another adaptors or linkers can be introduced on the fragments. Further, manipulations can be carried which prepare suitable restriction cleavage sides or remove the excess DNA or restriction cleavage sites. Where insertions, deletions or substitutions such as, for example transitions and transversions, are to be carried out, in vitro mutagenesis, primer repair, restrictions or ligations can be used. For methods of analysis, in general a sequence analysis, restriction analysis and other biochemical molecular biological methods can be used. After each manipulation, the DNA sequence used can be cleaved and bound with another DNA sequence. Each plasmid sequence can be cloned in the same or different plasmids.

Derivatives or parts of the DNA sequences and plasmids of the invention can also be used for the transformation of prokaryotic and eukaryotic cells. Further, the DNA sequences of the invention can be used according to standard processes for the isolation of similar sequences on the genome of plants of various species, which also code for sucrose or other oligosaccharide transporter molecules. With these sequences, constructs for the transformation of plant cells can be prepared which modify the transport process in transgenic plants.

In order to specify related DNA sequences, gene libraries must first be prepared, which are representative of the content in genes of a plant type or of the expression of genes in a plant type. The former are genomic libraries, while the latter are cDNA libraries. From these, related sequences can be isolated using the DNA sequences of the invention as probes. Once the related gene has been identified and isolated, a determination of the sequence and an analysis of the properties of the proteins coded from this sequence is possible.

In order to understand the examples forming the basis of this invention all the processes necessary for these tests and which are known per se will first be listed:

1. Cloning process

For cloning, there was used the phage Lambda ZAP II, as well as the vector pBluescriptSK (Short et al., 1988, Nucl Acids Res 16: 7583-7600).

For the transformation of yeasts, the vectors YIplac 128 and YEplac 112 (Gietz & Sugino, 1988, Gene 74: 527-534) were used.

For the plant transformation, the gene constructs in the binary vector pBinAR (Hofgen & Willmitzer, 1990, Plant Sci 66: 221-230) were cloned.

2. Bacterial and yeast strains

For the pBbluescriptSK vector as well as for PBinAR constructs, the E. coli strain XLlblue (Bullock et al., 1987, Biotechniques, 5, 376-378) was used.

As starting strain for the production of yeast strain YSH 2.64-1A-susy of the invention, the strain YSH 2.64-1A (Gozalbo & Hohmann, 1990, Curr Genet 17: 77-79) was used.

The transformation of the plasmid in potato plant was carried out using Agrobacterium tumefaciens strain LBA4404 (Bevan (1984) Nucl. Acids Res 12: 8711-8720).

3. Transformation of Agrobacterium tumefaciens

The transfer of the DNA in the Agrobacteria was carried out by direct transformation by the method of Hofgen & Willmitzer (1988, Nucleic Acids Res 16: 9877). The plasmid DNA of the transformed Agrobacterium was isolated in accordance with the method of Birnboim and Doly (1979) (Nucl Acids Res 7: 1513-1523) and was analysed by gel electrophoresis after suitable restriction cleavage.

4. Plant transformation

Ten small leaves, wounded with a scalpel, of a sterile potato culture were placed in 10 ml of MS medium with 2% sucrose containing 30-50 μl of an Agrobacterium tumefaciens overnight culture grown under selection. After 3-5 minutes gentle shaking, the leaves were laid out on MS medium of 1.6% glucose, 2 mg/l of zeatin ribose, 0.02 mg/l of naphthylacetic acid, 0.02 mg/l of gibberellic acid, 500 mg/l of claforan, 50 mg/l of kanamycin and 0.8% bacto agar. After incubation for one week at 25° C. and 3000 lux, the claforan concentration in the medium was reduced by half.

Deposits

The following plasmids and yeast strains were deposited at the Deutschen Sammlung yon Mikroorganismen (DSM) in Braunschweig, Germany on the 12.06.1992 (deposit number):

    ______________________________________                                         Plasmid     pSK-S21       (DSM 7115)                                           Yeast strain                                                                               YSH 2.64-1A-SUSY                                                                             (DSM 7106)                                           Yeast strain                                                                               YSH 2.64-1A-INV                                                                              (DSM 7105)                                           ______________________________________                                    

Description of the Figures

FIG. 1

Time pattern of the uptake of sucrose in yeast cells. "pmol/mg cells"=amount of the ¹⁴ C-labelled sucrose in pmol taken up in relation to the moisture weight of the yeast cells per mg; "112"=starting strain (without transporter); "+Glucose"=pre-incubation of the cells in a medium of 10 mM glucose; "-Glucose"=no pre-incubation of the cells; "2.5 μMCCCP"=coincubation with the inhibitor, carbonyl cyanide m-chlorophenylhydrazone (CCCP) in a concentration of 2.5 μM; "500 μMPCMBS"=coincubation with the inhibitor p-chloromercuribenzenesulfonic acid (PCMBS) in a concentration of 500 μM; "10 μM Antimycin"=coincubation with the inhibitor antimycin in a concentration of 10 μM.

FIG. 2

Cloning of the plasmid pMA5-INV. Shows the insertion of 2.4 kb size HindIII Fragment from pSEYC 306-1 in pMA5-10

FIG. 3

shows the plasmid pBinAR-S21.

    ______________________________________                                         In this::                                                                      CaMV 35S promoter:                                                                              promoter of the gene for the                                                   35S RNA of the cauliflower                                                     mosaic virus                                                  A:               coding region of the sucrose                                                   transporter in spinach,                                                        orientation in the reading                                                     direction                                                     OCS:             terminator of the octopine                                                     synthase gene from                                                             Agrobacterium tumefaciens                                     SmaI, NotI, BamHI:                                                                              Cleavage positions of                                                          restriction enzymes                                           ______________________________________                                    

FIG. 4

shows the plasmid pBinAR-P62-anti.

    ______________________________________                                         In this::                                                                      CaMV 35S promoter:                                                                               promoter of the gene for the                                                   35S RNA of the cauliflower                                                     mosaic virus                                                 OCS:              terminator of the octopine                                                     synthase gene from                                                             Agrobacterium tumefaciens                                    SmaI, SacI, BamHI, XbaI:                                                                         Cleavage positions of                                                          restriction enzymes                                          ______________________________________                                    

FIG. 5

Content of various carbohydrates in leaves of BinAR-P62-anti transformands.

    ______________________________________                                         In this                                                                        fru:        fructose                                                           suc:        sucrose                                                            sta:        starch                                                             control:    untransformed starting plants                                      sp-5 to sp-43:                                                                             transformands with individual numbers                              ______________________________________                                    

FIG. 6

Efflux of carbohydrates from petioles of BinAR-P62-anti transformands

    ______________________________________                                         wt:         Wild type                                                          sp-5 to sp-43:                                                                             transformands with individual numbers                              ______________________________________                                    

The following examples describe the preparation of the yeast strains, the identification as well as the function and use of a plant sucrose transporter.

EXAMPLE 1 Preparation of the yeast strains YSH 2.64-1A-SUSY and YSH 2.64-1A-INV

The yeast strain YSH 2.64-1A has the features suc2-, mal0, leu2, trpl (Gozalbo & Hohmann, 1990, Curr Genet 17: 77-79). In order to introduce sucrose cleaving enzymatic activity in this strain, it was transformed with the integrative plasmid YIplac128A2-SUSY, that contains the coding region of the sucrose synthase from potato as a fusion to the promoter of the gene for alcohol dehydrogenase from yeast. The plasmid YIplac 128A2-SUSY was prepared as follows. The plasmid YIplac128 (Gietz & Sugino, 1988, Gene 74: 527-534) was shortened by cleavage with PstI and EcoRI, degradation and/or filling in of overhanging single strands and ligation in the region of the polylinker. In the remaining SphI cleavage position, a 728 bp cassette was inserted with the promoter of alcohol dehydrogenase from the plasmid pVT102U (Vernet et al., 1987, Gene 52: 225-233). In this way YIplac128A2 was obtained. The coding region of the sucrose synthase was amplified by polymerase chain reaction with the oligonucleotides ##STR2## to a lambda clone of sucrose synthase from potato (Salanoubat & Belliard, 1987, Gene 60: 47-56). From the product, the coding region was prepared as BamHI fragment and inserted in the BamHI cleavage site of the polylinker of the cassette. The yeast strain YSH 2.64-1A was transformed with the so prepared plasmid YIplac128A2-SUSY. Since the plasmid does not carry the 2μ region, it cannot be autonomically replicated in yeast. Therefore such transformands only acquire leucine auxotrophy, which at least partially chromosomally integrate the plasmid-DNA.

Leucine autotroph colonies were analysed for expression of the sucrose synthase gene. For this, cells of a 5 ml liquid culture were decomposed by addition of glass pearls with vigorous shaking, and then, after centrifuging, total protein from the supernatant was added for an enzyme activity measurement. The activity of the expressed sucrose synthase contains 25 mU/mg protein.

In a similar manner an invertase activity was introduced in the yeast strain YSH 2.64-1A, in which by help of the plasmid YIplac128A1-INV, a gene for a cytosolic, noncleavable invertase was chromosomally integrated in the yeast genome. YIplac128A1-INV contains instead of the coding region for sucrose synthase, an invertase gene, which lacks the signal sequence for export of the gene product. The precursor of the plasmid is the plasmid YIplac128A1, which differs from YIplac128A2 in the orientation of the polylinker in the cassette with the promoter of the alcohol dehydrogenase gene. The cassette for this plasmid derives from the plasmid pVT100U (Vernet et al., 1987, Gene 52: 225-233). The coding region of the invertase was obtained on the DNA of the suc2 gene by polymerase chain reaction with the oligonucleotides INV3 (GAGCTGCAGATGGCAAACGAAACTAGCGATAGACCTTTGGTCACA) and INV4 (GAGACTAGTTTATAACCTCTATTTTACTTCCCTTACTTGGAA). The coding region was ligated as PstI/Spei fragment in the linearised vector YIplac128A1den using Psti and XbaI. A test of the enzymatic activity of the invertase activity expressed in the yeast cells, resulted in an enzyme activity of 68 mU/mg total protein from yeast cells.

EXAMPLE 2 Cloning of the cDNA plant sucrose transporter

From polyadenylated RNA from leaf tissue of growing spinach and potato plants, a library of the cDNA in the phage Lambda ZAP II library was prepared. From 500,000 Pfu, the phage DNA was prepared and purified using a caesium chloride sarcosyl gradient. After cleaving the phage DNA with the enzyme NotI, insertions from the size regions above and below 1.5 kbp were prepared on a 1% agarose gel and ligated in the NotI cleavage sites of the expressions vector YEplac112A1NE. The vector is a derivative of the vector YEplac 112 (Gozalbo & Hohmann, 1990, Curr Genet 17: 77-79), with which, as described in Example 1, the polylinker was exchanged with a cassette with the promoter of the alcohol dehydrogenase gene. The polylinker of the cassette was again removed by cleavage with the enzymes PstI and XbaI and replaced by a double stranded oligonucleotide that introduces a NotI and EcoRI cleavage site (Sequence: GATCCGCGGCCGCCCGGAATTCTCTAGACTGCA).

Approximately 90,000 clones for the size region below 1.5 kbp and approximately 40,000 clones for the size region above 1.5 kbp were obtained by transformation in E. coli. From these, plasmid DNA was prepared. 2 μg DNA was transformed fourteen times in the yeast strain YSH2.64-1A suc-.susy. Transformands were grown on a medium containing 2% glucose, and five to ten thousand of each were washed off with agar plate liquid medium and plated out on sucrose containing medium. Those colonies, which could be grown faster were further analysed. The insertion in the vector YEplac112A1NE of transformands S21 or P62 (YEplac112A1NE-S21) were sequenced. The sequences are given above

EXAMPLE 3 Analysis of sucrose metabolising yeast transformands

The yeast transformand YEplac112A1NE-S21, corresponding to that obtained in Example 2, was grown in liquid medium until the culture had reached the logarithmic phase. After centrifuging the culture, the cells were subjected to a pre-incubation for 5 minutes in a glucose containing medium and then taken up in a medium containing ¹⁴ C-labelled sucrose. The uptake of the labelled sucrose was measured by the process described by Cirillo (1989, Meth Enzymol 174: 617-622). The uptake of the labelled sucrose without preincubation with glucose was compared with that with co-incubation with the inhibitors carbonyl cyanide m-chlorophenylhydrazone (CCCP), p-chloromercuribenzenesulfonic acid (PCMBS) and antimycin. The time pattern is shown in FIG. 1. The calculated reduction of the sucrose uptake by the inhibitors is shown in table I. A competition experiment with various sugars as competitor for the labelled sucrose, from which the specificity of the transporter can be read off, is shown in table II.

Analogous measurements were carried out with the yeast strain YEplac112A1NE-P62. These gave similar results.

EXAMPLE 4 Transformation of bacterial strains with DNA sequences for expression of a sucrose transporter activity

In order to be able to metabolise taken-up sucrose, bacterial cells are needed which have an enzymatic activity for cleavage of the monosaccharide. To introduce such an activity, bacteria were transformed by the plasmid pMA5-INV and tested for invertase activity. The plasmid pMA5-INV was prepared as follows. The plasmid pMA5-10 (Stanssens et al., 1989, Nucl Acids Res 17: 4441-4454) was linearised at the HindIII cleavage site of the polylinker. The 2.4 kb HindIII fragment of the plasmid pSEYC306-1 (Taussig & Carlson, 1983, Nucl Acids Res 11: 1943-1954) was cloned in the HindIII cleavage site. The corresponding cutout of the plasmid is shown in FIG. 2. The enzymatic activity of the invertase in bacteria cells, transformed with the plasmid pMA5-INV was determined in a gel electrophoresis activity test, in known manner. The possibility of the formation of a functional sucrose transporter though expression of a plant cDNA in bacteria cells was tested by transformation of E. coli with the plasmid pSK-S21. The plasmid is described Example 3. After transformation of bacteria cells with pSK-S21, tests for sucrose uptake were carried out.

EXAMPLE 5 Transformation of plants with a construct for over-expression of the coding region of the sucrose transporter

From the vectors YEplac 112A1NE-S21 and YEplac 112A1NE-P62, which contain, as inserts, the cDNA for the sucrose transporter from spinach and/or potato (see Examples 2 and 3), the inserts after NotI cleavage were isolated and ligated in the NotI cleavage site of the plasmids pBluescript-SK (pSK-S21 and/or pSK-P62). For pSK-S21, the insert was prepared as a SacI/XbaI fragment and cloned, after filling in the overhanging single strand-DNA, in the "sense" orientation in pBinAR (Hofgen & Willmitzer, 1990, Plant Sci 66: 221-230) which was previously cleaved with the enzymes SmaI and XbaI. The resulting plasmid pBinAR-S21 (see FIG. 3) can be inserted for transformation of plants in order to over-express the sucrose transporter. For pSK-P62, the insert was isolated as a 1.7 kbp NotI fragment and cloned in an "antisense" orientation in the SmaI cleavage site of the binary vector pBinAR, resulting in pBinAR-P62-anti (see FIG. 4). This plasmid is suitable for transformation of plants with the aim of "antisense" inhibition of the expression of the sucrose transporter.

Transformation Agrobacteria were then used for infection of leaf segments of tobacco and potato.

In ten independently obtained transformands, in which the presence of the intact, non-rearranged chimeric gene was demonstrated by Southern blot analysis, changes in sucrose, hexose and starch content were respectively tested.

Transformands, which contain the T-DNA from pBinAR-P62-anti, showed a strongly increased concentration of starches, hexoses and sucrose in the leaves (see FIG. 5). The efflux of carbohydrate from the petioles taken from the plants is greatly reduced in aqueous medium (see FIG. 6). From these data, the significance of the sucrose transporter for the transport away of the photoassimilate from the photosynthetically active organs is clearly seen. Since an inhibition of the activity of the transporter limits the transport away of carbohydrates, this results from a lowering of the transfer of photoassimilates to storage organs in the case of an over-expression, for example using the plasmid pBinAR-S21. Tobacco plants, in which the T-DNA from pBinAR-S21 has been integrated, show further a reduced apical dominance, i.e. they show a bushy growth. Such a phenotypical change is, for example, very desirable in tomato plants. The plasmid pBinAR-S21 with the DNA sequence (Seq. ID No. 1) of the invention is therefore suited for the modification of plants with the purpose of improving important breeding characteristics such as bushy growth.

                  TABLE I                                                          ______________________________________                                                         sucrose transport*                                             Inhibitor       (%)                                                            ______________________________________                                         Control         100                                                            0.5 μM CCCP  65                                                             2.5 μM CCCP  21                                                             25 μM PCMBS  73                                                             100 μM PCMBS 21                                                             25 μM 2,4-DNP                                                                               61                                                             100 μM 2,4-DNP                                                                              9                                                              1 mM sodium arsenate                                                                           34                                                             10 μM antimycin A                                                                           59                                                             1 m cAMP        102                                                            ______________________________________                                          CCCP = carbonyl cyanide mchlorophenylhydrazone                                 PCMBS = pchloromercuribenzenesulfonic acid                                     2,4DNP = 2,4dinitrophenol                                                      *= in relation to Y Eplac 112 A1NES21 (control)                          

                  TABLE II                                                         ______________________________________                                                          sucrose transport*                                            Competitor       (%)                                                           ______________________________________                                         Control          100                                                           2 mM sucrose     28                                                            2 mM maltose     58                                                            10 mM maltose    37                                                            2 mM phenylglucoside                                                                            7                                                             2 mM phloridzin  16                                                            2 mM lactose     91                                                            10 mM palatinose 102                                                           10 mM trehalose  103                                                           ______________________________________                                          *= in relation to YEplac 112 A1NE  S21 (control)                         

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 4                                                   (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1969 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Spinacia oleracea                                                (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 70..1644                                                         (D) OTHER INFORMATION: /note="Sucrose-Transporter"                             (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        AAAAACACACACCCAAAAAAAAAACACTACGACTATTTCAAAAAAAACATTGTTACTAGA60                 AATCTTATTATGGCAGGAAGAAATATAAAAAATGGTGAAAATAACAAG108                            MetAlaGlyArgAsnIleLysAsnGlyGluAsnAsnLys                                        1510                                                                           ATTGCGGGTTCTTCTCTTCACTTAGAGAAGAACCCAACAACTCCCCCC156                            IleAlaGlySerSerLeuHisLeuGluLysAsnProThrThrProPro                               152025                                                                         GAGGCCGAGGCTACCTTAAAGAAGCTCGGCCTCGTGGCTTCAGTAGCG204                            GluAlaGluAlaThrLeuLysLysLeuGlyLeuValAlaSerValAla                               30354045                                                                       GCCGGGGTTCAGTTCGGGTGGGCTTTACAGCTCTCCCTACTGACCCCG252                            AlaGlyValGlnPheGlyTrpAlaLeuGlnLeuSerLeuLeuThrPro                               505560                                                                         TACGTCCAACTACTGGGCATTCCCCACACTTGGGCCGCCTACATCTGG300                            TyrValGlnLeuLeuGlyIleProHisThrTrpAlaAlaTyrIleTrp                               657075                                                                         TTGTGCGGCCCAATCTCGGGGATGATTGTCCAGCCATTGGTCGGGTAC348                            LeuCysGlyProIleSerGlyMetIleValGlnProLeuValGlyTyr                               808590                                                                         TATAGTGACCGGTGCACCTCCCGCTTCGGCCGACGTCGCCCCTTCATT396                            TyrSerAspArgCysThrSerArgPheGlyArgArgArgProPheIle                               95100105                                                                       GCAGCAGGGGCGGCTCTAGTGGCCGTAGCGGTGGGGCTAATCGGATTC444                            AlaAlaGlyAlaAlaLeuValAlaValAlaValGlyLeuIleGlyPhe                               110115120125                                                                   GCCGCCGATATCGGCGCAGCGTCGGGTGATCCAACGGGAAACGTGGCA492                            AlaAlaAspIleGlyAlaAlaSerGlyAspProThrGlyAsnValAla                               130135140                                                                      AAACCCCGGGCCATCGCGGTGTTTGTGGTCGGGTTTTGGATCCTCGAC540                            LysProArgAlaIleAlaValPheValValGlyPheTrpIleLeuAsp                               145150155                                                                      GTGGCTAACAACACCCTGCAAGGCCCATGCAGGGCGTTGTTAGCAGAC588                            ValAlaAsnAsnThrLeuGlnGlyProCysArgAlaLeuLeuAlaAsp                               160165170                                                                      ATGGCCGCCGGGTCGCAAACCAAAACCCGGTACGCTAACGCCTTCTTC636                            MetAlaAlaGlySerGlnThrLysThrArgTyrAlaAsnAlaPhePhe                               175180185                                                                      TCCTTCTTCATGGCGTTAGGAAACATCGGAGGGTACGCCGCCGGTTCA684                            SerPhePheMetAlaLeuGlyAsnIleGlyGlyTyrAlaAlaGlySer                               190195200205                                                                   TACAGCCGCCTCTACACGGTGTTCCCCTTTACCAAAACCGCCGCCTGC732                            TyrSerArgLeuTyrThrValPheProPheThrLysThrAlaAlaCys                               210215220                                                                      GACGTCTACTGCGCCAATCTAAAATCCTGCTTCTTCATCTCCATCACA780                            AspValTyrCysAlaAsnLeuLysSerCysPhePheIleSerIleThr                               225230235                                                                      CTCCTAATCGTCCTCACAATCCTAGCACTTTCCGTCGTAAAAGAGCGT828                            LeuLeuIleValLeuThrIleLeuAlaLeuSerValValLysGluArg                               240245250                                                                      CAAATCACAATCGACGAAATCCAAGAAGAAGAAGACTTAAAAAACAGA876                            GlnIleThrIleAspGluIleGlnGluGluGluAspLeuLysAsnArg                               255260265                                                                      AACAATAGCAGCGGTTGTGCAAGACTACCGTTCTTCGGACAATTAATA924                            AsnAsnSerSerGlyCysAlaArgLeuProPhePheGlyGlnLeuIle                               270275280285                                                                   GGCGCTCTCAAAGATCTACCAAAACCAATGCTAATCCTATTACTAGTA972                            GlyAlaLeuLysAspLeuProLysProMetLeuIleLeuLeuLeuVal                               290295300                                                                      ACAGCCCTAAATTGGATCGCATGGTTTCCATTCTTGTTGTTCGATACT1020                           ThrAlaLeuAsnTrpIleAlaTrpPheProPheLeuLeuPheAspThr                               305310315                                                                      GATTGGATGGGTAAAGAAGTGTACGGTGGTACAGTCGGAGAAGGTAAA1068                           AspTrpMetGlyLysGluValTyrGlyGlyThrValGlyGluGlyLys                               320325330                                                                      TTGTACGACCAAGGAGTTCATGCCGGTGCCTTAGGTCTGATGATTAAC1116                           LeuTyrAspGlnGlyValHisAlaGlyAlaLeuGlyLeuMetIleAsn                               335340345                                                                      TCCGTTGTCTTAGGTGTTATGTCGTTGAGTATTGAAGGTTTGGCTCGT1164                           SerValValLeuGlyValMetSerLeuSerIleGluGlyLeuAlaArg                               350355360365                                                                   ATGGTAGGCGGTGCTAAAAGGTTATGGGGAATTGTCAATATTATTCTT1212                           MetValGlyGlyAlaLysArgLeuTrpGlyIleValAsnIleIleLeu                               370375380                                                                      GCTGTTTGTTTAGCTATGACGGTGTTAGTTACTAAGTCCGCCGAACAC1260                           AlaValCysLeuAlaMetThrValLeuValThrLysSerAlaGluHis                               385390395                                                                      TTCCGTGATAGCCACCATATTATGGGCTCCGCCGTCCCTCCGCCGCCG1308                           PheArgAspSerHisHisIleMetGlySerAlaValProProProPro                               400405410                                                                      CCTGCTGGTGTTAAGGGTGGCGCTTTGGCTATCTTTGCCGTTCTTGGT1356                           ProAlaGlyValLysGlyGlyAlaLeuAlaIlePheAlaValLeuGly                               415420425                                                                      ATCCCTCTTGCGATCACTTTCAGTATTCCTTTGGCCTTGGCGTCAATC1404                           IleProLeuAlaIleThrPheSerIleProLeuAlaLeuAlaSerIle                               430435440445                                                                   TTTTCAGCATCTTCCGGTTCAGGACAAGGTCTTTCTCTAGGAGTTCTC1452                           PheSerAlaSerSerGlySerGlyGlnGlyLeuSerLeuGlyValLeu                               450455460                                                                      AACCTCGCCATCGTTGTACCCCAGATGTTTGTGTCGGTAACAAGTGGG1500                           AsnLeuAlaIleValValProGlnMetPheValSerValThrSerGly                               465470475                                                                      CCATGGGATGCAATGTTTGGTGGAGGAAATTTGCCAGCATTCGTGGTG1548                           ProTrpAspAlaMetPheGlyGlyGlyAsnLeuProAlaPheValVal                               480485490                                                                      GGAGCTGTAGCAGCAACAGCCAGTGCAGTTCTTTCATTTACATTGTTG1596                           GlyAlaValAlaAlaThrAlaSerAlaValLeuSerPheThrLeuLeu                               495500505                                                                      CCTTCTCCACCCCCTGAAGCTAAAATTGGTGGGTCCATGGGTGGTCAT1644                           ProSerProProProGluAlaLysIleGlyGlySerMetGlyGlyHis                               510515520525                                                                   TAAGAAATTTAATACTACTCCGTACAATTTAAACCCAAATTAAAAATGAAAATGAAAATT1704               TTTAACCCATGTTCGTTACGTTGTAATTAGAGAGAAAAATGATATATTGAACGAAGCCGT1764               TAATTTATGCTCCGTTCATCTTGTAATTCTTTTTCTCTCTGCTTTTTTTTTTTTTTTTTA1824               ACGCGACGTGTTTTTGAGATAAGGAAGGGCTAGATCGAGGATGGGGGAATTGGCAAGAAA1884               TTGCTCGGGTATAAATATTTATCCCTCTTTGTAATTTTCAGTAACATTTAATAGCCAGAA1944               ATCAAAAAGTCAAGAAAAATCGAAA1969                                                  (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 525 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        MetAlaGlyArgAsnIleLysAsnGlyGluAsnAsnLysIleAlaGly                               151015                                                                         SerSerLeuHisLeuGluLysAsnProThrThrProProGluAlaGlu                               202530                                                                         AlaThrLeuLysLysLeuGlyLeuValAlaSerValAlaAlaGlyVal                               354045                                                                         GlnPheGlyTrpAlaLeuGlnLeuSerLeuLeuThrProTyrValGln                               505560                                                                         LeuLeuGlyIleProHisThrTrpAlaAlaTyrIleTrpLeuCysGly                               65707580                                                                       ProIleSerGlyMetIleValGlnProLeuValGlyTyrTyrSerAsp                               859095                                                                         ArgCysThrSerArgPheGlyArgArgArgProPheIleAlaAlaGly                               100105110                                                                      AlaAlaLeuValAlaValAlaValGlyLeuIleGlyPheAlaAlaAsp                               115120125                                                                      IleGlyAlaAlaSerGlyAspProThrGlyAsnValAlaLysProArg                               130135140                                                                      AlaIleAlaValPheValValGlyPheTrpIleLeuAspValAlaAsn                               145150155160                                                                   AsnThrLeuGlnGlyProCysArgAlaLeuLeuAlaAspMetAlaAla                               165170175                                                                      GlySerGlnThrLysThrArgTyrAlaAsnAlaPhePheSerPhePhe                               180185190                                                                      MetAlaLeuGlyAsnIleGlyGlyTyrAlaAlaGlySerTyrSerArg                               195200205                                                                      LeuTyrThrValPheProPheThrLysThrAlaAlaCysAspValTyr                               210215220                                                                      CysAlaAsnLeuLysSerCysPhePheIleSerIleThrLeuLeuIle                               225230235240                                                                   ValLeuThrIleLeuAlaLeuSerValValLysGluArgGlnIleThr                               245250255                                                                      IleAspGluIleGlnGluGluGluAspLeuLysAsnArgAsnAsnSer                               260265270                                                                      SerGlyCysAlaArgLeuProPhePheGlyGlnLeuIleGlyAlaLeu                               275280285                                                                      LysAspLeuProLysProMetLeuIleLeuLeuLeuValThrAlaLeu                               290295300                                                                      AsnTrpIleAlaTrpPheProPheLeuLeuPheAspThrAspTrpMet                               305310315320                                                                   GlyLysGluValTyrGlyGlyThrValGlyGluGlyLysLeuTyrAsp                               325330335                                                                      GlnGlyValHisAlaGlyAlaLeuGlyLeuMetIleAsnSerValVal                               340345350                                                                      LeuGlyValMetSerLeuSerIleGluGlyLeuAlaArgMetValGly                               355360365                                                                      GlyAlaLysArgLeuTrpGlyIleValAsnIleIleLeuAlaValCys                               370375380                                                                      LeuAlaMetThrValLeuValThrLysSerAlaGluHisPheArgAsp                               385390395400                                                                   SerHisHisIleMetGlySerAlaValProProProProProAlaGly                               405410415                                                                      ValLysGlyGlyAlaLeuAlaIlePheAlaValLeuGlyIleProLeu                               420425430                                                                      AlaIleThrPheSerIleProLeuAlaLeuAlaSerIlePheSerAla                               435440445                                                                      SerSerGlySerGlyGlnGlyLeuSerLeuGlyValLeuAsnLeuAla                               450455460                                                                      IleValValProGlnMetPheValSerValThrSerGlyProTrpAsp                               465470475480                                                                   AlaMetPheGlyGlyGlyAsnLeuProAlaPheValValGlyAlaVal                               485490495                                                                      AlaAlaThrAlaSerAlaValLeuSerPheThrLeuLeuProSerPro                               500505510                                                                      ProProGluAlaLysIleGlyGlySerMetGlyGlyHis                                        515520525                                                                      (2) INFORMATION FOR SEQ ID NO:3:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 1773 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (vi) ORIGINAL SOURCE:                                                          (A) ORGANISM: Solanum tuberosum                                                (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 5..1552                                                          (D) OTHER INFORMATION: /note="Sucrose-Transporter"                             (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                        AAAAATGGAGAATGGTACAAAAAGAGAAGGTTTAGGGAAACTTACAGTT49                            MetGluAsnGlyThrLysArgGluGlyLeuGlyLysLeuThrVal                                  151015                                                                         TCATCTTCTCTACAAGTTGAACAGCCTTTAGCACCATCAAAGCTATGG97                             SerSerSerLeuGlnValGluGlnProLeuAlaProSerLysLeuTrp                               202530                                                                         AAAATTATAGTTGTAGCTTCCATAGCTGCTGGTGTTCAATTTGGTTGG145                            LysIleIleValValAlaSerIleAlaAlaGlyValGlnPheGlyTrp                               354045                                                                         GCTCTTCAGCTCTCTTTGCTTACACCTTATGTTCAATTGCTCGGAATT193                            AlaLeuGlnLeuSerLeuLeuThrProTyrValGlnLeuLeuGlyIle                               505560                                                                         CCTCATAAATTTGCCTCTTTTATTTGGCTTTGTGGACCGATTTCTGGT241                            ProHisLysPheAlaSerPheIleTrpLeuCysGlyProIleSerGly                               657075                                                                         ATGATTGTTCAGCCAGTTGTCGGCTACTACAGTGATAATTGCTCCTCC289                            MetIleValGlnProValValGlyTyrTyrSerAspAsnCysSerSer                               80859095                                                                       CGTTTCGGTCGCCGCCGGCCATTCATTGCCGCCGGAGCTGCACTTGTT337                            ArgPheGlyArgArgArgProPheIleAlaAlaGlyAlaAlaLeuVal                               100105110                                                                      ATGATTGCGGTTTTCCTCATCGGATTCGCCGCCGACCTTGGTCACGCC385                            MetIleAlaValPheLeuIleGlyPheAlaAlaAspLeuGlyHisAla                               115120125                                                                      TCCGGTGACACTCTCGGAAAAGGATTTAAGCCACGTGCCATTGCCGTT433                            SerGlyAspThrLeuGlyLysGlyPheLysProArgAlaIleAlaVal                               130135140                                                                      TTCGTCGTCGGCTTTTGGATCCTTGATGTTGCTAACAACATGTTACAG481                            PheValValGlyPheTrpIleLeuAspValAlaAsnAsnMetLeuGln                               145150155                                                                      GGCCCATGCAGAGCACTACTGGCTGATCTCTCCGGCGGAAAATCCGGC529                            GlyProCysArgAlaLeuLeuAlaAspLeuSerGlyGlyLysSerGly                               160165170175                                                                   AGGATGAGAACAGCAAATGCTTTTTTCTCATTCTTCATGGCCGTCGGA577                            ArgMetArgThrAlaAsnAlaPhePheSerPhePheMetAlaValGly                               180185190                                                                      AACATTCTGGGGTACGCCGCCGGTTCATATTCTCACCTCTTTAAAGTA625                            AsnIleLeuGlyTyrAlaAlaGlySerTyrSerHisLeuPheLysVal                               195200205                                                                      TTCCCCTTCTCAAAAACCAAAGCCTGCGACATGTACTGCGCAAATCTG673                            PheProPheSerLysThrLysAlaCysAspMetTyrCysAlaAsnLeu                               210215220                                                                      AAGAGTTGTTTCTTCATCGCTATATTCCTTTTACTCAGCTTAACAACC721                            LysSerCysPhePheIleAlaIlePheLeuLeuLeuSerLeuThrThr                               225230235                                                                      ATAGCCTTAACCTTAGTCCGGGAAAACGAGCTCCCGGAGAAAGACGAG769                            IleAlaLeuThrLeuValArgGluAsnGluLeuProGluLysAspGlu                               240245250255                                                                   CAAGAAATCGACGAGAAATTAGCCGGCGCCGGAAAATCGAAAGTACCG817                            GlnGluIleAspGluLysLeuAlaGlyAlaGlyLysSerLysValPro                               260265270                                                                      TTTTTCGGTGAAATTTTTGGGGCTTTGAAAGAATTACCTCGACCGATG865                            PhePheGlyGluIlePheGlyAlaLeuLysGluLeuProArgProMet                               275280285                                                                      TGGATTCTTCTATTAGTAACCTGTTTGAACTGGATCGCGTGGTTTCCC913                            TrpIleLeuLeuLeuValThrCysLeuAsnTrpIleAlaTrpPhePro                               290295300                                                                      TTTTTCTTATACGATACAGATTGGATGGCTAAGGAGGTTTTCGGTGGA961                            PhePheLeuTyrAspThrAspTrpMetAlaLysGluValPheGlyGly                               305310315                                                                      CAAGTCGGTGATGCGAGGTTGTACGATTTGGGTGTACGCGCTGGTGCA1009                           GlnValGlyAspAlaArgLeuTyrAspLeuGlyValArgAlaGlyAla                               320325330335                                                                   ATGGGATTACTGTTGCAATCTGTGGTTCTAGGGTTTATGTCACTTGGG1057                           MetGlyLeuLeuLeuGlnSerValValLeuGlyPheMetSerLeuGly                               340345350                                                                      GTTGAATTCTTAGGGAAGAAGATTGGTGGTGCTAAGAGGTTATGGGGA1105                           ValGluPheLeuGlyLysLysIleGlyGlyAlaLysArgLeuTrpGly                               355360365                                                                      ATTTTGAACTTTGTTTTGGCTATTTGCTTGGCTATGACCATTTTGGTC1153                           IleLeuAsnPheValLeuAlaIleCysLeuAlaMetThrIleLeuVal                               370375380                                                                      ACCAAAATGGCCGAGAAATCTCGCCAGCACGACCCCGCCGGCACACTT1201                           ThrLysMetAlaGluLysSerArgGlnHisAspProAlaGlyThrLeu                               385390395                                                                      ATGGGGCCGACGCCTGGTGTTAAAATCGGTGCCTTGCTTCTCTTTGCC1249                           MetGlyProThrProGlyValLysIleGlyAlaLeuLeuLeuPheAla                               400405410415                                                                   GCCCTTGGTATTCCTCTTGCGGCAACTTTTAGTATTCCATTTGCTTTG1297                           AlaLeuGlyIleProLeuAlaAlaThrPheSerIleProPheAlaLeu                               420425430                                                                      GCATCTATATTTTCTAGTAATCGTGGTTCAGGACAAGGTTTGTCACTA1345                           AlaSerIlePheSerSerAsnArgGlySerGlyGlnGlyLeuSerLeu                               435440445                                                                      GGAGTGCTCAATCTTGCAATTGTTGTACCACAGATGTTGGTGTCACTA1393                           GlyValLeuAsnLeuAlaIleValValProGlnMetLeuValSerLeu                               450455460                                                                      GTAGGAGGGCCATGGGATGATTTGTTTGGAGGAGGAAACTTGCCTGGA1441                           ValGlyGlyProTrpAspAspLeuPheGlyGlyGlyAsnLeuProGly                               465470475                                                                      TTTGTAGTTGGAGCAGTTGCAGCTGCCGCGAGCGCTGTTTTAGCACTC1489                           PheValValGlyAlaValAlaAlaAlaAlaSerAlaValLeuAlaLeu                               480485490495                                                                   ACAATGTTGCCATCTCCACCTGCTGATGCTAAGCCAGCAGTCGCCATG1537                           ThrMetLeuProSerProProAlaAspAlaLysProAlaValAlaMet                               500505510                                                                      GGGCTTTCCATTAAATAATTACAAAAGAAGGAGAAGAACAACTTTTTTTTAATAT1592                    GlyLeuSerIleLys                                                                515                                                                            TAGTACTTCTCTTTTGTAAACTTTTTTTATTTTAGAAAACAAACATAACATGGAGGCTAT1652               CTTTACAAGTGGCATGTCCATGTATCTTCCTTTTTTCATAAAGCTCTTTAGTGGAAGAAG1712               AATTAGAGGAAGTTTCCTTTTAATTTCTTCCAAACAAATGGGGTATGTGTAGTTGTTTTC1772               A1773                                                                          (2) INFORMATION FOR SEQ ID NO:4:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 516 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                        MetGluAsnGlyThrLysArgGluGlyLeuGlyLysLeuThrValSer                               151015                                                                         SerSerLeuGlnValGluGlnProLeuAlaProSerLysLeuTrpLys                               202530                                                                         IleIleValValAlaSerIleAlaAlaGlyValGlnPheGlyTrpAla                               354045                                                                         LeuGlnLeuSerLeuLeuThrProTyrValGlnLeuLeuGlyIlePro                               505560                                                                         HisLysPheAlaSerPheIleTrpLeuCysGlyProIleSerGlyMet                               65707580                                                                       IleValGlnProValValGlyTyrTyrSerAspAsnCysSerSerArg                               859095                                                                         PheGlyArgArgArgProPheIleAlaAlaGlyAlaAlaLeuValMet                               100105110                                                                      IleAlaValPheLeuIleGlyPheAlaAlaAspLeuGlyHisAlaSer                               115120125                                                                      GlyAspThrLeuGlyLysGlyPheLysProArgAlaIleAlaValPhe                               130135140                                                                      ValValGlyPheTrpIleLeuAspValAlaAsnAsnMetLeuGlnGly                               145150155160                                                                   ProCysArgAlaLeuLeuAlaAspLeuSerGlyGlyLysSerGlyArg                               165170175                                                                      MetArgThrAlaAsnAlaPhePheSerPhePheMetAlaValGlyAsn                               180185190                                                                      IleLeuGlyTyrAlaAlaGlySerTyrSerHisLeuPheLysValPhe                               195200205                                                                      ProPheSerLysThrLysAlaCysAspMetTyrCysAlaAsnLeuLys                               210215220                                                                      SerCysPhePheIleAlaIlePheLeuLeuLeuSerLeuThrThrIle                               225230235240                                                                   AlaLeuThrLeuValArgGluAsnGluLeuProGluLysAspGluGln                               245250255                                                                      GluIleAspGluLysLeuAlaGlyAlaGlyLysSerLysValProPhe                               260265270                                                                      PheGlyGluIlePheGlyAlaLeuLysGluLeuProArgProMetTrp                               275280285                                                                      IleLeuLeuLeuValThrCysLeuAsnTrpIleAlaTrpPheProPhe                               290295300                                                                      PheLeuTyrAspThrAspTrpMetAlaLysGluValPheGlyGlyGln                               305310315320                                                                   ValGlyAspAlaArgLeuTyrAspLeuGlyValArgAlaGlyAlaMet                               325330335                                                                      GlyLeuLeuLeuGlnSerValValLeuGlyPheMetSerLeuGlyVal                               340345350                                                                      GluPheLeuGlyLysLysIleGlyGlyAlaLysArgLeuTrpGlyIle                               355360365                                                                      LeuAsnPheValLeuAlaIleCysLeuAlaMetThrIleLeuValThr                               370375380                                                                      LysMetAlaGluLysSerArgGlnHisAspProAlaGlyThrLeuMet                               385390395400                                                                   GlyProThrProGlyValLysIleGlyAlaLeuLeuLeuPheAlaAla                               405410415                                                                      LeuGlyIleProLeuAlaAlaThrPheSerIleProPheAlaLeuAla                               420425430                                                                      SerIlePheSerSerAsnArgGlySerGlyGlnGlyLeuSerLeuGly                               435440445                                                                      ValLeuAsnLeuAlaIleValValProGlnMetLeuValSerLeuVal                               450455460                                                                      GlyGlyProTrpAspAspLeuPheGlyGlyGlyAsnLeuProGlyPhe                               465470475480                                                                   ValValGlyAlaValAlaAlaAlaAlaSerAlaValLeuAlaLeuThr                               485490495                                                                      MetLeuProSerProProAlaAspAlaLysProAlaValAlaMetGly                               500505510                                                                      LeuSerIleLys                                                                   515                                                                            __________________________________________________________________________ 

We claim:
 1. An isolated DNA sequence comprising the coding region of an oligosaccharide transporter gene derived from a potato or spinach plant.
 2. A DNA sequence according to claim 1, wherein said sequence comprises the following nucleotide sequence (Seq-ID No 1): ##STR3##
 3. A DNA sequence according to claim 1, wherein said sequence comprises the following nucleotide sequence (Seq-ID No 3): ##STR4##
 4. A plasmid, comprising a DNA sequence according to claim
 1. 5. An isolated DNA sequence, according to claim 1, wherein integration and expression of said sequence into a plant or a plant cell alters the formation and transport of storage materials in said plant or said plant cell relative to a non-transformed plant or plant cell.
 6. A method of producing plant cells with oligosaccharide transporter activity, comprising the step of transforming plant cells with a plasmid according to claim
 4. 7. A transgenic plant comprising an altered amount of oligosaccharide transporter activity relative to a non-transformed plant, said plant comprising the DNA sequence of claim
 1. 8. A plant or plant cell transformed with a plasmid according to claim 4, wherein said plant or plant cell is capable of expressing an altered amount of oligosaccharide transporter activity relative to a non-transformed plant.
 9. A method of producing a plant cell with an increased synthesis of sucrose transporter relative to a non-transformed plant, comprising the steps of:producing a DNA molecule comprising the following sequences:i) a promoter which is active in said plant or plant cell, ii) a structural DNA sequence, according to claim 1, which allows the transcription of an RNA which in said transgenic plant codes for an oligosaccharide transporter; and transferring and incorporating said DNA molecule into the genome of a plant cell.
 10. A recombinant expression vector comprising a DNA sequence encoding an oligosaccharide transporter derived from a potato or spinach plant and a promoter sequence, wherein the promoter is capable of expressing the oligosaccharide transporter gene in a transformed plant cell or transgenic plant.
 11. A method of over-expressing an oligosaccharide transporter gene, comprising the step of transforming a plant or a plant cell with plasmid pBin-AR-S21 prepared from plasmid pSK-S21.
 12. A method of altering the characteristics of agriculturally useful plants, comprising the step of transforming an agriculturally useful plant with a DNA sequence according to claim
 1. 13. A plasmid comprising a coding portion of the DNA sequence according to claim
 2. 14. A plasmid comprising a coding portion of the DNA sequence according to claim
 3. 15. A method of altering the characteristics of an agriculturally useful plant, comprising the step of transforming an agriculturally useful plant with a DNA sequence according to claim
 2. 16. A method of altering the characteristics of an agriculturally useful plant, comprising the step of transforming an agriculturally useful plant with a DNA sequence according to claim
 3. 